This is the username used by the global rename tool when renaming users. Normally, when a user is renamed, the user who performed the rename will appear in the logs as having both renamed the user and moved the user's userpages to their new name. If the user performing the rename does not have an attached local account on the wiki, this username will be shown in the logs instead.
The global rename script is not a bot and is unaffected by blocks.
Any issues with this script should be reported on Phabricator.